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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 916 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 93° and angle B = 34°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  5. 5.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  6. 6.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 4 cm, 5 cm and 2 cm? (a) No (b) Yes
  8. 8.Can a triangle have sides of 10 cm, 12 cm and 27 cm? (a) Yes (b) No
  9. 9.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  10. 10.In triangle ABC, angle A = 78° and angle B = 62°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  12. 12.Can a triangle have sides of 8 cm, 5 cm and 3 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 44° and angle B = 31°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  18. 18.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  22. 22.Can a triangle have sides of 6 cm, 3 cm and 3 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 25° and angle B = 37°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 78° and angle B = 81°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 61° and 20°. What is the exterior angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  28. 28.In triangle ABC, angle A = 40° and angle B = 114°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 72° and 51°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 35° and 78°. What is the exterior angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  35. 35.In triangle ABC, angle A = 65° and angle B = 44°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  38. 38.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 75
  2. 36
  3. 53
  4. 57
  5. 16
  6. 41
  7. Yes
  8. No
  9. 24
  10. 40
  11. 54
  12. No
  13. 58
  14. 105
  15. 100
  16. 78
  17. 13
  18. 13
  19. 100
  20. 54
  21. 40
  22. No
  23. 33
  24. 118
  25. 21
  26. 81
  27. 8
  28. 26
  29. 19
  30. 123
  31. 74
  32. 72
  33. 113
  34. 25
  35. 71
  36. 64
  37. 77
  38. 20
  39. 14
  40. 36

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